WAGO 750-495/040-00 Series Manual page 50

50 Function Description
The specified observation interval for this can be set using the number of half-
waves (WAGO-I/O-CHECK or registers 43, 44 and 45).
Arithmetic mean, min/max values and the peak value are not available for the
neutral conductor current.
Line-to-line voltages are calculated on the basis of the phase voltages and the
corresponding phase angles (with "3-Wire Wye/Delta," 2 line-to-line voltages are
measured directly and the third line-to-line voltage is calculated).
Calculation of power
Individual, synchronous sampling values for current and voltage are used for
calculating active power (P). Phase shifts between the currents and voltages are
taken into account in the power calculation. Positive values occur when the
power is "exhausted" by a load, i.e., the current has a phase shift of −90° ... +90°
relative to the voltage (operation under load, quadrants I and IV). Negative values
occur when the power is "fed in" by a generator, i.e., the current has a phase shift
of 90° ... 270° relative to the voltage (generator operation, quadrants II and III).
See the figure "4-Quadrant Representation of Active and Reactive Power."
In the event of negative power values, verify correct connection of voltage
transformer, current transformer or Rogowski coil
If power measurements erroneously yield negative power values, check whether
you have connected the corresponding voltage transformer, current transformer
or Rogowski coil in the correct orientation.
Active power minimum and maximum values are determined over a configurable
time interval (WAGO-I/O-CHECK or parameters 37, 38 and 39).
In real networks, not all loads are purely resistive. Phase shifting occurs between
the current and voltage. However, this does not affect the method for determining
the RMS values for current and voltage previously described. The I/O module
calculates both the reactive power (Q) and the apparent power (S) for each
phase.
The total effective power (P), total reactive power (Q) and total apparent power
(S) are calculated as follows:
P = P1 + P2 + P3 (with "3-Wire Wye/Delta": P
total
Q = Q1 + Q2 + Q3 (with "3-Wire Wye/Delta": Q
total
S = S1 + S2 + S3
total
These calculations are only performed in WAGO-I/O-CHECK and CODESYS
function blocks and cannot be exported through the process image.
Manual
Version 1.2.0
750-495/040-00x 3-Phase Power Measurement Module 690 V
WAGO-I/O-SYSTEM 750 XTR
= P1 + P3)
total
= Q1 + Q3)
total